ASS68, Motorola M 6800 Cross-Assembler

      The  attached  cross-assembler  was  written   for   a
PDP11-45  running  under the RSX11M operating system.  It is
written in DEC's FORTRAN IV PLUS and may not  be  transferr-
able to other systems without modification.

      Note particularly the use of INTEGER*2 values for  the
bytes and INTEGER*4 values for addresses so as to avoid hav-
ing to do anything about negative values!  Another thing  is
that in many places BYTE arrays (LOGICAL*1) are EQUIVALENCED
to bigger elements so as  to  allow  character  loading  and
string comparisons.  This is OK on most machines but beware,
the PDP bytes are arranged in a different order in  a  word.
for bytes 1,2,3 etc a PDP11 word contains
    INTEGER*2     byte2 byte1
    INTEGER*4     byte4 byte3 byte2 byte1

Whereas an IBM word is the opposite
    INTEGER*4     byte1 byte2 byte3 byte4

Beware too, DEC FORTRAN IV where although 4 bytes  are  res-
erved  for  INTEGER*4 variables, they are only treated as if
they  were  INTEGER*2.   Better  to  use  REAL  for  strings
throughout  if  theres  a doubt, but maybe it will work with
your FORTRAN.

      BEST OF LUCK.


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